Sunan an-Nasa'i 3855
سنن النسائي#3855Sahihأَخْبَرَنَا نُوحُ بْنُ حَبِيبٍ، قَالَ أَنْبَأَنَا عَبْدُ الرَّزَّاقِ، قَالَ أَنْبَأَنَا مَعْمَرٌ، عَنِ ابْنِ طَاوُسٍ، عَنْ أَبِيهِ، عَنْ أَبِي هُرَيْرَةَ، قَالَ قَالَ رَسُولُ اللَّهِ صلى الله عليه وسلم " مَنْ حَلَفَ عَلَى يَمِينٍ فَقَالَ إِنْ شَاءَ اللَّهُ فَقَدِ اسْتَثْنَى " .
It was narrated that Abu Hurairah said:"The Messenger of Allah said: 'Whoever swears an oath and says: "If Allah wills, then he has made an exception
Scholarly Authentication
The label above is the grade most of these scholars gave — one dissenting opinion no longer speaks for all of them. If any scholar calls a narration fabricated, that verdict is shown instead, whatever the others say. Each scholar's own wording:
Abu GhuddahSahih
Al-AlbaniSahih
Zubair Ali ZaiIsnaad Sahih
In-book reference: 35:95